Railway brake shoes are typically mounted on brake rigging of railway vehicles by means of a brake shoe key, which passes through a longitudinal slot in the brake shoe holder or "brakehead" of the brake rigging and concurrently through mounting holes of the brake shoe backing plate. Such holes are normally located in a central "keybridge" area of the brake shoe backing plate. The keybridge area of the backing plate is generally formed in such a way that it is adapted to protrude into or intersect with a longitudinal slot in the brakehead at or near the center of the brakehead's length.
A certain type of railroad transit vehicle utilizes brake shoes made of a solid processed wooden material and having a different mounting system. Such shoes are mounted to the brakehead by means of brass screws which project through the face of the brakehead and are embedded into the body of the brake shoe. Wooden shoes have been used on these vehicles because, heretofore, other types of composition brake shoes have caused excessive brake squeal when the brake was applied to the wheels of these vehicles. The noise tendency is related to the unique shape of the wheel and the suspension of the wheel, which is used primarily for the braking function and does not normally contact a rail surface during operation. The wooden type of brake shoe has been found most resistant to noise generation, and the existing mounting arrangement has been reliable for the wooden type of brake shoe, although it has several disadvantages. These include a time consuming assembly process which requires the use of power tools and reduction in useable thickness of the brake shoe in order to avoid contact between the screw and the wheel as the brake shoe wears.
While new composition materials have been developed which have acceptable noise characteristics, these types of material have mechanical properties different than wood, such that the screw mounting system is not as reliable as when used with wooden brake shoes. It also has been recognized that the depth of the screws require the brake shoe to be replaced while there is still significant thickness of material on the brake shoe, which could otherwise contribute to a longer useable life of the brake shoe. Therefore, an alternate design of the mounting system was desired.